1. Field of Invention
The present invention relates to novel chiral polymers comprising a peralkyl cyclodextrin bound to polysiloxane by means of a single spacer arm and the use of such polymers as chiral stationary phases in analytical and preparative gas, supercritical fluid and liquid chromatographic separations. More particularly, this invention relates to novel chiral polymers a peralkylated cyclodextrin, preferably a .beta.-cyclodextrin, bound to a linear polysiloxane by means of a single spacer arm which can have various lengths and compositions. This invention also relates to the use of these cyclodextrin containing polysiloxane polymers for analysis of enantiomeric and other stereoisomeric mixtures of various substances. This invention relates as well to the use of either open tubular column surface-bonded or packed column particle-bound chiral cyclodextrin polymeric siloxane materials, prepared by coating and immobilizing by chemical reaction or heating the chiral polymeric siloxanes on the desired column or particle surface for gas, supercritical fluid and liquid chromatography separations, and the separation of enantiomeric and other stereoisomeric mixtures of various structures using these materials.
2. Prior Art
Analytical separation of enantiomers has become very important in light of interest in the resolution and enantiomeric purity of drugs. Chem. Eng. News, 1990, Mar. 19, 38; Stinson, S.C. Chem. Eng. News, 1992, Sep. 28, 46. The use of chiral stationary phases (CSPs) in chromatography is the most convenient method to determine enantiomeric purity. Allenmark, S. G. Chromatographic Enantioseparations: Methods and Applications, 2nd ed., Prentice Hall, N.J., 19991. In recent years, the use of O-derivatized cyclodextrins as CSPs in capillary gas chromatography (GC) and supercritical fluid chromatography (SFC) has become a powerful tool in modern enantiomer analysis. Schurig, et al., Angew. Chem. Int. Ed. Engl. 1990, 29, 939; Koen de Vries et al., J. High Resolut. Chromatogr. 1992, 15, 499; Dietrich, et al., J. High Resolut. Chromatogr. 1992, 15, 590; Reiher, et al., J. High Resolut. Chromatogr. 1992, 15, 346 and Schurig, et al., J. High Resolut. Chromatogr. 1991, 14, 58. Most of the stationary phases derived from cyclodextrin are prepared by diluting the relevant cyclodextrin derivative in polysiloxane in order to obtain selective chiral separations at temperatures below the melting point of the pure cyclodextrin derivative. The state of the art in this field has been reviewed by Schurig, et al., Angew. Chem. Int. Ed. Engl. 1990, 29, 939. A few cyclodextrin stationary phases have been prepared by chemically bonding permethylated alkenyl-substituted .beta.-cyclodextrin to a polysiloxane backbone by a hydrosilylation reaction. Schurig, et al., J. High Resolut. Chromatogr. 1991, 14, 58; Schurig, et al., J. High Resolut. Chromatogr. 1990, 13, 713 and Fischer, et al., Angew. Chem. Int. Ed. Engl. 1990, 29, 427. In these cases, the permethylated alkenyl-substituted .beta.-cyclodextrins were a mixture of cyclodextrins containing 1-7 alkenyl group(s) on the rim of the cyclodextrin instead of a pure monoalkenyl-substituted compound. Because the number of connecting alkenyl groups on the rim of the cyclodextrin may vary from molecule to molecule, reproducibility or uniformity of product is not assured from batch to batch and results of separations of enantiomers may also vary.
Chiral copolymers, wherein the chiral portion of the copolymer can be a cyclodextrin are disclosed and claimed in copending patent application Ser. No. 07/878,157 filed May 4, 1992 which has been allowed and is awaiting issuance.